(1−x)NiFe<inf>2</inf>O<inf>4</inf>/xZnMn<inf>2</inf>O<inf>4</inf> solid solution: structure and dielectric properties investigation

Abstract

(1−x)NiFe2O4/xZnMn2O4 solid solution samples were prepared by the sol–gel method. Rietveld analysis of X-ray diffraction data obtained for the samples manifested that all samples have a single-phase NiFe2O4 (NFO) cubic spinel structure, inferring that Mn and Zn ions are incorporated into the NiFe2O4 matrix making a solid solution (Ni/Zn)[Fe/Mn]2O4. XPS measurements confirmed the existence of Zn and Mn cations in the obtained solid solutions. The effect of Zn and Mn incorporation on the lattice parameter, crystallite size, bond angle and length of NFO phase was studied in detail. TEM images demonstrated a symmetrical particle morphology with nearly spherical shape in the nanorange. The variations of the dielectric constant, dielectric loss, electric impedance, electric modulus and ac electrical conductivity with the temperature, frequency, and the parameter (x) were examined employing the impedance spectroscopy technique. Samples with x = 0.1 or 0.25 have a higher conductivity as compared with the pristine NFO sample. All samples followed large polaron tunneling (OLPT) except sample with x = 0.25; it followed two mechanisms: the small polaron (SP) at low temperatures and the OLPT at higher temperatures.